Bioremediation has emerged as a promising technology for the treatment of soil and groundwater contamination. Some conventional bioremediation approaches require the soil to be excavated for treatment either off site or ex-situ. Disadvantages of these approaches include disruption of the natural field and the need to transport large quantities of contaminated soil.
It would be beneficial to establish a bioremediation system in-situ in the field and without the need for transporting the contaminated soil or water. Methods for bioremediation in the field can use certain bacteria which digest and neutralize contaminants. Often, these bacteria are provided as a liquid culture. In these methods, water is used as a carrier to deliver bacteria and/or nutrients to the treatment area in the field. However, utilizing water as a medium to deliver and distribute bacteria is associated with various problems. Bacteria require moisture. However, simple liquid or water cultures in-situ cannot maintain sufficiently the moisture level because water tends to evaporate and this causes massive losses in potential microbial activity. Hence, establishing and sustaining sufficiently large microbial populations at the contamination site becomes problematic.
Bacteria obtain from their environment all nutrient materials necessary for their metabolic processes and cell reproduction. The food must be in solution and must pass into the cell. This is especially difficult when treating contamination in-situ due to high levels of toxicity being present at the start of a treatment and the lack of food that is inevitable towards the end of the process. Further, aerobes need oxygen for respiration and cannot grow unless oxygen is provided. Additionally, bacteria have a pH range within which growth is possible. Although the optimum pH value differs between species, an environment that is maintained to a neutral pH will best sustain most bacterial species utilized for in-situ bioremediation.
Successful bioremediation requires optimizing biomass in-situ, as this represents the total amount of suitable bacteria present in a given area or volume that will have the potential to metabolize and break down the contamination in order to remediate the targeted area of pollution.
The fate of in-situ bioremediation is generally considered to be uncertain when utilizing water as a medium to distribute bacteria because water is fluid and it is difficult to localize the distribution and delivery to one area. The process may become wasteful and massive amounts of bacterial inoculate may be lost through natural migration. Moreover, much of the bacteria often misses the targeted pollution entirely, as the liquid culture passes through the soil too quickly to allow the formation of molecular bonds that are essential to both establishing and sustaining an effective process of biodegradation.
Thus, there remains the need in the field for compositions and methods of delivering bacteria and other microorganisms in-situ for bioremediation of land and water.